the only way to repopulate the cart without being logged in is to store the cart in a cookies.
in the eCart object, change the Store In option from Session to Cookies
Be aware though that cookies have certain limitations. the user wont be able to add items to the cart on one computer, then use another computer, or even a different browser to re populate the cart. Cookies also have a maximum size. After so many items are added to the cart, the cart will not accept any additional items. This max size is different in different browsers.